Timeline

BOSTON, April 19 (Reuters) - Police emptied the streets of suburban Watertown on Friday in a house-by-house search for a second suspect in the Boston Marathon bombing, after killing his brother in a shootout.
The night of shooting and explosions in the streets followed the authorities' release on Thursday of video footage of the two suspects.
Here is a timeline of events:

Thursday, about 5:10 p.m.
The FBI releases photographs and video of two men suspected of planting the pressure cooker bombs that killed three people and injured 176 at the Boston Marathon on Monday. Video footage shows a man known as suspect No. 1 wearing a dark baseball cap. He was later identified as Tamerlan Tsarnaev, 26.
Suspect No. 2, later identified as Tsarnaev's brother, Dzhokhar, 19, was wearing a white cap backwards in the images. The 30-second videos are played repeatedly on national television, and photographs of the suspects are posted online.

Thursday night at 9:04 p.m.
Russian language social networking site VK shows someone logged for the last time out of what appears to be Dzhokhar Tsarnaev's page. The site had been accessed via mobile device.

Thursday night around 10:20 p.m.
Two men rob a convenience store at the Massachusetts Institute of Technology campus. Shortly after, shots are fired in the area.

10:30 p.m.
Police discover MIT campus police officer Sean Collier, 26, shot multiple times in his car in an apparent confrontation with the suspects. He was transported to Massachusetts General Hospital and pronounced dead.

Shortly after 10:30 p.m.
Police say the two brothers carjack a Mercedes SUV. The owner of the car is held hostage for about a half hour and is then released. Police chase the SUV into the Boston suburb of Watertown. During the chase, the suspects throw explosives from the car and exchange gunfire with police.

A transit police officer is hurt in the shootout. Witnesses report hearing dozens of gunshots.

Tamerlan Tsarnaev is hit during the shootout. He is taken into custody, transported to Beth Israel Deaconess Medical Center and later pronounced dead.

Before 1 a.m. Friday
A huge manhunt is launched for the second suspect and hundreds of police officers and FBI agents descend on Watertown.

Between 3 and 4 a.m.
Massachusetts police announce they will conduct a door-to-door search in Watertown. Citizens are warned to stay indoors.

Around 5:30 a.m.
Train service in Boston is suspended.

8 a.m.
Massachusetts officials announce they have expanded the shelter-in-place recommendations for the entire city of Boston, effectively putting the city in lockdown as they search for Tsarnaev.

10:30 a.m.
Police say they have located a gray Honda CRV with Massachusetts license plates in the Boston area that they believe had been occupied by a Boston Marathon bombing suspect.

Shortly after 10:45 a.m.
Top security and counterterrorism advisers finish an hourlong briefing with President Barack Obama in the White House Situation Room on developments in the Boston manhunt.
Compiled based on media reports, official statements from law enforcement and Reuters reporting. All times Eastern Daylight Time.

BOSTON - One suspected Boston Marathon bomber was killed early Friday morning and police are hunting the other in Watertown, Mass., after the suspects killed an MIT police officer and wounded a Massachusetts Bay Transportation Authority officer in a wild chase that involved explosives and gunfire, authorities said.

"We believe this to be a terrorist," Boston police Commissioner Ed Davis said. "We believe this to be a man who came here to kill people."

All of Boston, Watertown, Cambridge, Newton, Waltham and Belmont are under a "shelter-in-place" order, with orders for all residents to stay home with doors locked. Do not open the door for anyone other than a licensed law enforcement officer, said Gov. Deval Patrick. The entire MBTA system has been shut down.

SWAT teams, machine guns drawn, were going door-to-door in Watertown. Blood was found behind one building and a police chemist was testing it.

The suspects were identified to The Associated Press as coming from the Russian region near Chechnya, which has been plagued by an Islamic insurgency stemming from separatist wars. A law enforcement intelligence bulletin obtained by the AP identified the surviving bomb suspect as Dzhokhar A. Tsarnaev, a 19-year-old who had been living in Cambridge, just outside Boston, and said he "may be armed and dangerous."

A man who described himself as an uncle, Ruslan Tsarni of Maryland, said the suspects are brothers who have been in the country since 2001.

When his wife showed him the picture of the suspects, he was "shaking."

"Anger, anger, anger. I can't come up with the words," Tsarni said when asked for his response to the terrorist attacks his nephews are accused of. "Unhuman."

A man who described himself as a friend of the suspects, Ahdi Moro, 22, of Watertown, said the two attended Cambridge Rindge & Latin School.

"I was pretty shocked," Moro said. "I would never think anything like that of them. They were good kids."

He said the older brother was a Golden Gloves boxer who is now the father of a 2-year-old and Dzhokhar was an all-star wrestler.

"He was a really quiet kid," Moro said. "He was very popular at school, like, the most popular kid at school. He was a really good-looking kid. He's as American as anybody. He grew up here. He's like a regular Cambridge kid."

He said the older brother was big and tough, and remembered how, on the first day of school, he was "picked on" by three kids _ and beat up all three.

"These kids grew up around violence," Moro said. "They were always not scared of anything."

State Police Col. Timothy Alben said the slain man was Suspect No. 1 in Monday's Boston Marathon bombings and the man police are seeking is Suspect No. 2, the man in the white hat seen in images released Thursday by the FBI. The fugitive was described as armed and dangerous, as police set a 20-block perimeter bordered by Arsenal Street and Mount Auburn Avenue. All vehicular traffic has been banned in Watertown.

A new photo of the man thought to be Suspect No. 2, taken from store video in a Cambridge 7-Eleven Friday night, showed him in a gray hoodie sweatshirt.

The chaotic, violent chain of events began with a report of shots fired on the MIT campus at about 10:20 p.m. Friday, according to a narrative released by the Middlesex District Attorney's office.

At 10:30 p.m., an MIT campus police officer was found with multiple gunshot wounds in his vehicle near Vassar and Main streets. He was pronounced dead at Massachusetts General Hospital.

Police then received reports of a carjacking at gunpoint by two men in the area of Third Street in Cambridge. The driver was held in the car by the suspects for about a half hour before he was released unharmed at a gas station on Memorial Drive.

Dozens of police who had converged on the initial MIT scene near Kendall Square after the shooting raced toward Watertown shortly before 1 a.m. Police had tried to pull over a carjacked vehicle, resulting in one suspect shot and 33-year-old MBTA officer Richard H. Donahue Jr. wounded. A manhunt was launched for the suspect who fled, with heavily armed SWAT teams and uniformed cops with their handguns drawn spreading through the area.

One suspect was critically injured in the course of the chase and died in a local hospital.

Police in Watertown were shouting warnings that the suspects were "throwing explosives," and warned about "unexploded ordinance" on the street.

Marylynn Martin, 24, who lives in Watertown, was sleeping with her 4-year-old son and 1-year-old daughter in the pre-dawn hours.

"First I heard the gunshots and then I heard the explosion," Martin said. "All of a sudden police swarmed the area, so I came out and they told me to get back in. They were swearing. 'Get the (expletive) inside!' I looked out back and there were 20 officers. It was upsetting to see SWAT and police everywhere."

Friday morning while the search continued, and warnings for people to stay inside were repeated, the State Police Bomb Squad was at work removing possible explosive devices believed to have been thrown from the car in Watertown.

___

Earlier reports continue bellow.

Officer Shot

As local authorities pursued the suspects, at least one of the individuals tried to hurl explosive devices at police, according to the federal official. At that point, agents from the Federal Bureau of Investigation and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives joined the manhunt.

When police confronted the suspects, a gun battle ensued. A second officer, from the transit police, was shot and is in serious condition, according to David Procopio, a Massachusetts State Police spokesman. As the chase continued through Watertown, the FBI released two additional images of the men it said were tied to the marathon bombing.

President Barack Obama was briefed overnight by his counterterrorism adviser, Lisa Monaco, about the events in Boston and Watertown, according to a White House official who commented on condition of not being identified.

Suspect Dead

Police brought one of the suspects, an adult male with multiple gunshot wounds and an injury consistent with an explosion, to Beth Israel Deaconess Medical Center at 1:20 a.m., Dr. Richard Wolfe, chief of emergency medicine, told reporters at a news conference held with the hospital's chief executive officer, Dr. Kevin Tabb.

The patient, whose name Tabb wouldn't release, was pronounced dead at 1:35 a.m. local time after efforts to resuscitate him failed.

Beth Israel cared for 24 of the injured from the bombings. Twelve remain in the hospital, one of them in serious condition, Tabb said.

Dr. David Schoenfeld, who worked on the injured male early this morning before he died, told reporters he was home in Watertown last night catching up on paperwork. When he heard the gunfire and explosions outside, he headed to the hospital to help with what he assumed were casualties headed to Beth Israel.

'Two Shooters'

Andrew Kitzenberg, a Watertown resident, said he witnessed from his bedroom window a confrontation between two men in a black SUV and police.

"There were two shooters with handguns," he told MSNBC. They also had "what seemed to be grenades" and "what looked to be a pressure cooker bomb," referring to the type of explosive device that the marathon attackers are thought to have used.

As an explosion went off, one of the shooters ran toward officers, and "went down," Kitzenberg said. The second shooter got in the SUV and "floored it" in the direction of the officers.

Police had issued warnings over their radio about "multiple explosive devices." People in the area were told to stay off mobile phones to avoid setting off any potential bombs. At least one loud explosion was heard.

This morning, police carrying assault rifles swept through Watertown, where people were warned to stay inside their homes. A message from state police on the Twitter social network urged residents not to open their doors unless it's an identifiable law enforcement officer.

Transit Shutdown

The Massachusetts Bay Transportation Authority has been shut down, Boston police said, as officers continue to hunt for the suspect who escaped during a gun battle in Watertown.

Police streamed into the area from many local towns, as did law-enforcement officers from the FBI, transit authority and the National Guard. Multiple ambulances were standing by.

Reports of chases and sightings in nearby areas sent streams of police cars careering through the narrow streets. Officers converged with spotlights and guns drawn.

Watertown resident Larry Victor described the scene: "Tons and tons and tons of gunfire. Explosions. What a wild event right here in Watertown. I wasn't about to walk out in the middle of a gun battle."

One man in Watertown was ordered by police to strip naked and then taken into custody. Police had surrounded the man with their guns drawn, ordered him to the ground and shouted. "Drop your underwear!"

It was not immediately known whether the man had any involvement in the overnight violence or the marathon bombing.

'Multiple Gunshots'

"Our daughter woke us up and said there were a lot of gunshots," said one witness, Scott Price.

The family heard multiple gunshots, he said. "You could smell the gunpowder." Price's wife, Anne, said they heard three explosions. "It was very frightening," she said. "Our daughter was very scared."

Shortly before 2 a.m. local time, a half dozen Boston and state police, some carrying assault rifles, ran past a group of construction workers at Dana-Farber Cancer Institute, across the street from Beth Israel Deaconess Medical Center, yelling "active shooter, active shooter" and urging the workers to get inside, said Michael Hartley, one of the workers. The police ran toward Children's Hospital, Hartley said.

At Beth Israel, city and state police cruisers, their lights flashing, stood by. A state police officer shooed a reporter off the hospital grounds, declining to answer questions.

MIT Officer

The MIT officer who was shot last night was responding to reports of a disturbance on campus, according to a statement from Middlesex Acting District Attorney Michael Pelgro. The officer, who wasn't identified, was found with multiple gunshot wounds and taken to a hospital, where he was pronounced dead, Pelgro said.

Gunshots were heard on the campus at about 10:48 p.m. local time last night near the Ray and Maria Stata Center, and people have been asked to stay clear of the area, according to a statement posted on the university's website. MIT later issued an all-clear.

Officers from state and local law enforcement units were on the campus shooting scene, along with some personnel wearing FBI jackets. Two police dogs were seen sniffing around a building marked the McGovern Institute for Brain Research.

About 20 police vehicles with lights flashing were seen along Vassar Street at MIT, which was cordoned off with yellow crime-scene tape. A police boat with lights flashing was patrolling the nearby Charles River, and a helicopter hovered over the campus.

The Cambridge Police Department issued a message of condolences through a posting on the Twitter social network.

"Our thoughts & prayers are with the officer's family & our brothers & sisters at the #MIT Police," the Cambridge police said.